The invention relates to a process and apparatus for attaching specifically tapelike strips such as labels to containers where the strips are separated individually from a supply stack and fed to the containers after having been provided with a heat-seal coating.
In connection with applying labels, film cuts or other strips to containers such as bottles, cold glues are commonly used. Most cold glues are based on dextrin, casein or starch. These materials are inexpensive and can be processed at room temperatures without any trouble. Initially, the adhesion is relatively low, however, so that large contact surfaces are required between label and container for preventing slippage of the label during subsequent brush-on. Cold glues are unsuitable for bonding to metallic surfaces. The so-called heat-seal or thermoplastic adhesives, which for processing purposes must be heated substantially above room temperature, have a substantially higher adhesive power. They are more expensive than cold glues but they are not wholly trouble free and they require expensive heating installations. Therefore, heat-seal adhesives are usually used only in special cases such as for the attaching of control tapes and labels to containers.
For example, there is a known process of the initially indicated type, where the labels are taken off of a supply stack by vacuum means and on their way to the containers are provided with a heat-seal adhesive coating after which they are pressed on with their center part to the container closure caps (U.S. Pat. No. 3,097,983). With this exclusively heat-seal using process the labels are seated -- despite their limited contact surface -- even on metallic closure caps in a relatively tight way and, therefore, can hardly slip off center during the further feeding and pressing on of both of their still projecting ends. A remaining disadvantage is that even under vacuum produced withdrawal conditions the labels can slip off center so a uniform appearance of containers and an accurate seating of labels cannot be guaranteed. Furthermore, vacuum operated withdrawal devices require substantial operating time and, hence, slow down production.
There is another known process for attaching file index labels to bottles where tapelike labels are withdrawn through adhesion to glue, are glued in the process and then pressed on to the bottles (DOS 2,055,417). With this process obviously involving the exclusive use of cold glue, the initial adhesive power of labels on the bottles is relatively low which requires a complicated press-on stage and a long, process delaying press-on time. Even so, this does not prevent a slippage of labels.